Thought my truck was on fire

[Rckdrummer]

Hello all,

I have a 72' GMC K15 SWB with an automatic TH 350 and I installed a new kickdown cable on it today. Out on the road test, everything went great at first, but then suddenly there was white smoke coming into the cab from the 4x4 shift boot just after the second time kickdown was engaged. I pulled over expecting the worst, but by the time I jumped out with the fire extinguisher there was no more smoke, or evidence of any fire. I pulled the shifter boot off and again, no smoke or evidence of fire there either. It started right back up and ran fine the half mile drive back.

Has anyone else experienced this? Apologies in advance if I've left out any necessary context, I'm still pretty shooken up.